The present application claims priority of German patent application 100 01 955.2, filed on Jan. 18, 2000, the disclosure content of which is hereby expressly also made the object of the present application.
The invention relates to an opto-electronic switch.
In almost all electric or electronic devices, manual operation is effected by switches. These switches are almost always designed mechanically, two metal parts being brought into contact or respectively out of contact in order to close or respectively to open a circuit. However, this mechanical design has the disadvantage, amongst others, that it has mechanical wearing parts and consequently only has a limited service life and is fundamentally water-sensitive such that, where required, a costly casing is necessary.
Optical switches are already known; however, up to now they have been extremely lavish and, consequently, expensive and do not yet have the required standard of operational reliability. However, in principle, optical switches have advantages, as they manage, generally speaking, without any moving mechanical parts and the switching process can be triggered by mere tapping or by contacting a control surface or simply through approximation to a sensor.
DE 42 07 772 makes known an opto-electronic switch, which, using a logic component, recognizes tapping as the displacement pattern and evaluates this as a switching pulse as long as the tapping, for example effected by a finger, lasts for a certain dwell time. This shall enable to distinguish especially between tapping and, for example, wiping over a ceramic hob. However, as the sensor switch does not recognize a change in dynamic movement, additional sensors are necessary as blocking sensors, which make the tapping of a finger distinguishable from larger objects and consequently have a negative influence on the cost and the size of the system.
DE 42 07 772 makes known an opto-electronic switch, which, using a logic component, recognizes tapping as the displacement pattern and evaluates this as a switching pulse as long as the tapping, for example effected by a finger, lasts for a certain dwell time. There must be a difference more especially between tapping and, for example, wiping over a ceramic hob. However, as the sensor switch does not recognize a change in dynamic movement, additional sensors are necessary as blocking sensors, which make the tapping of a finger distinguishable from larger objects and consequently have a negative influence on the cost and the size of the system.
U.S. Pat. No. 5,103,085 A makes known an opto-electronic switch, which, for example, is for recognizing the approximation of an object to the glass in a display window even in sunlight. If the sensor is covered statically for a time predetermined by a timer, a circuit for further actuation becomes connected. It is not possible with this to recognize a tapping process with the steps of approximationxe2x80x94dwelling for a short timexe2x80x94lifting. For this reason, other displacements can result in a triggering of the circuit.
WO-A 86/01953 also works to acquire a finger displacement with static signals. A threshold value is deposited in a sample and hold circuit. To keep this threshold value above the actual value, a slow time constant is used in such a manner that there is not sufficient dynamic range presentxe2x80x94if any at allxe2x80x94to recognize sudden, time-variable displacements.
PATENT ABSTRACTS OF JAPAN vol. 007, No. 266 (P-239), 26th November 1983 and JP 58 147670 make known an opto-electronic detection circuit, where for elimination of the detection sensitivity, a single signal is taken apart and a portion of the signal is supplied in a time-delayed manner to a comparator. The DC signal is then differentiated. Here it is not a question of the acquisition and above all not of the evaluation of a typical signal curve for a switching displacement.
DE 31 46 152 A1 describes an opto-electronic keyboard, which reacts to changes in the flow of photons. The evaluation units, which are not described in more detail, measure the change in intensity, which is produced in the flow of photons when the key is actuated, and trigger a switching process when the threshold values are exceeded. To increase the operating reliability, the keys respond in a time-delayed manner and recesses are provided for operation. There is no acquisition of time-variable changes in displacement.
DE 35 24 492 makes known coupling opto-electronic control elements to a pair of photoconductors. The transmitting photoconductor and the receiving photoconductor terminate under a resilient control element in such a manner that when the control element is actuated, the conditions of reflectance change and are evaluated as deliberate actuation. There is no acquisition of time-variable changes in displacement or differentiation between deliberate and accidental actuations by interrogating a displacement pattern, which comprises several steps. A comparable device working with a photoconductor is known in FR 2 693 859 A1.
DE 35 26 992 C2 proposes opto-electronic switching elements preferably for a ceramic hob, whereby objects such as, for example, a cookbook, accidentally placed on the surface, are not to trigger a switching process. To this end, as a time-variable change in displacement cannot be detected, the dwell time of an object on the switching element is checked for a relatively long time of up to 10 seconds and a switching process is only triggered if the dwell time is less. This may still be applicable to ceramic hobs, as it takes a certain time to supply the heat, however a shorter reaction time is necessary for normal switches.
DE 42 12 565 A1 also makes known an encased, mechanically operating foil keyboard. Snap-type washers are provided as the actuating element.
It is an object of the invention to create an improved opto-electronic switch, more especially an opto-electronic switch with a high degree of operational reliability.
These and other objects are achieved according to the invention by the provision of an opto-electronic switch including at least one light-emitting transmitting element having a radiation field, at least one receiving element for receiving light, the at least one receiving element outputting a first signal, a value of the first signal depending on the amount of light received, wherein the at least one light-emitting transmitting element and the at least one receiving element are disposed so that the light transmitted by the at least one light-emitting transmitting element is at least partially reflected by an object which is situated within a given region and which is spaced in a given manner from the at least one receiving element and transmitting element such that at least an amount of a reflected light reaches the at least one receiving element, and an evaluation unit for evaluating the first signal and including at least one switching element, wherein the evaluation unit determines a time-variable change in displacement of the object when the object is suddenly braked in a defined region, the time-variable change in displacement being a function of a change in the first signal, which change is caused by displacement of the object, the evaluation unit recognizing the time-variable displacement as tapping when the time-variable displacement is within a predetermined displacement pattern, and wherein the switching element changes from one switching state to another switching state if the displacement of the object creates an object displacement pattern lying within limits of the predetermined displacement pattern.